High mobility group protein-1 (HMG-1) is a unique activator of p53.
The binding of p53 protein to DNA is stimulated by its interaction with covalent as well as noncovalent modifiers. We report the identification of a factor from HeLa nuclear extracts that activates p53 DNA binding. This factor was purified to homogeneity and identified as the high mobility group protein, HMG-1. HMG-1 belongs to a family of highly conserved chromatin-associated nucleoproteins that bend DNA and facilitate the binding of various transcription factors to their cognate DNA sequences. We demonstrate that recombinant His-tagged HMG-1 enhances p53 DNA binding in vitro and also that HMG-1 and p53 can interact directly in vitro. Unexpectedly, HMG-1 also stimulates DNA binding by p53Delta30, a carboxy-terminally deleted form of the protein that is considered to be constitutively active, suggesting that HMG-1 stimulates p53 by a mechanism that is distinct from other known activators of p53. Finally, using transient transfection assays we show that HMG-1 can increase p53 and p53Delta30-mediated transactivation in vivo. HMG-1 promotes the assembly of higher order p53 nucleoprotein structures, and these data, along with the fact that HMG-1 is capable of bending DNA, suggest that HMG-1 may activate p53 DNA binding by a novel mechanism involving a structural change in the target DNA.
Jayaraman
L
L
Department of Biological Sciences, Columbia University, New York, New York 10027, USA.
Moorthy
N C
NC
Murthy
K G
KG
Manley
J L
JL
Bustin
M
M
Prives
C
C
D004247:DNA / Q000378:metabolism; D006367:HeLa Cells; D006609:High Mobility Group Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D008957:Models, Genetic; D009687:Nuclear Proteins / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D006609:High Mobility Group Proteins; D009687:Nuclear Proteins; D010446:Peptide Fragments; D011994:Recombinant Proteins; D016159:Tumor Suppressor Protein p53; D004247:DNA